The present invention relates to insulating sheets, and particularly to an insulating sheet suitable for a hard disk device.
A hard disk device (HDD) has disks with a recording layer formed on a surface, and comprises a head for writing to these disks, an arm for supporting the head, and an actuator for causing movement of the arm.
These disks are housed inside a case, and a printed wiring board for carrying out control of the actuator and input and output of data to and from the disks is located outside the case. FIG. 5 is a schematic cross sectional view of a HDD, with reference numeral 110 representing the actual HDD, reference numeral 111 representing the case of the HDD 110, and reference numeral 112 representing the printed wiring board. Electronic components are mounted on the printed wiring board 112 and an electronic circuit made up of these electronic components is connected to the bottom 117 of the actuator using a flexible wiring board 114.
An insulating sheet 113 is located between the printed wiring board 112 and the case 111, and the printed wiring board 112 is screwed to the case 111 in this state. The electronic circuit formed on the printed wiring board 112 is insulated from the case 111 by this insulating sheet 113.
The insulating sheet 113 has a buffer layer 121, an adhesive layer 122 and a resin film 123. The buffer layer 121 and the resin film 123 are glued together using the adhesive layer 122.
The adhesive layer 122 conventionally uses adhesive, and in order to maintain its characteristics, this film is supplied interposed between release liners 131 and 132, as shown in FIG. 6.
When this type of adhesive layer 122 is used, the release liner 131 is first torn off to expose one surface of the adhesive layer 122, and this exposed surface is pressed against the resin film 123. The adhesive layer 122 is a pressure sensitive resin and it will attach to the resin film 123 when the adhesive layer is pressed. Next, the other release liner 132 is torn off to expose the opposite surface of the adhesive layer 122. The adhesive layer 122 is pressed against the buffer layer 121. The resin film 123 and the buffer layer 121 will attach together by the adhesive layer 122, thus resulting in an insulating sheet 113.
Once the insulating sheet 113 is interposed between the printed wiring board 112 and the case 111, screw fastened, and the flexible wiring board 114 attached, the HDD 110 shown in FIG. 5 is completed.
As described above, with the HDD 110 of the related art, since the adhesive layer 122 is pressure sensitive and has adhesive properties at a normal temperature, the release liners 131 and 132 are indispensable when the adhesive layer 122 is rolled up for transportation or storage.
Since the release liners 131 and 132 are required to have a non-adhesive property, a material having silicone oil coated on the resin films as the base material of the release liners 131 and 132 is used. Therefore, a silicone component is attached to the adhesive layer 122, and if the silicone component is released from the insulating sheet 113 by generation of heat during driving of the HDD 110, this is likely to have a detrimental effect of the electronic circuit of the printed wiring board 112 and the electronic components inside the case 111.
Non-silicone type release liners are expensive and have poor applicability. Even if a non-silicone type release liner is adopted, it is necessary to dispose of the release liner, and this is not desirable from the point of view of reducing waste.
The present invention has been created in order to solve the above described drawbacks in the related art, and the object of the present invention is to provide an insulating sheet that does not release a silicone component.